The present invention relates generally to gas burners and, more particularly, to an improved ignition and flame sensing circuit for maintaining the continued presence of a flame.
In various gas powered appliances such as cooking ranges, water heaters and clothes dryers, flame sensors are typically provided in order to ensure continued flame presence after ignition. In the event that a flame is lost, ignition sparks are generated to effect reignition. One example of such an ignition/reignition circuit having a flame sensing capability is provided in U.S. Pat. No. 5,169,303 to Paluck, the disclosure of which is hereby incorporated herein by reference. Paluck teaches a type of flame sensing and reignition circuit for a gas burner which uses the same ignition electrode in providing the flame sensing as well as the ignition functions of the circuit.
While this design minimizes the total number of circuit components, certain compromises must be made, especially in determining the position of the ignition electrode. An optimum position of the electrode with respect to the burner for accomplishing ignition may result in an electrode position which is most susceptible to flame waver. Placing the electrode at a radial distance from the burner body which provides a sufficient spark gap for ignition may result in an electrode positioned too far from the burner to accurately sense a very low burning flame. A less than optimal flame sensing position can result in errant determinations of flame absence which in turn causes nuisance sparking or the generation of reignition sparks in the continued presence of the flame.
The ignition and flame sensing circuit of the present invention provides an improvement over prior circuits of this type in that separate flame sensing and reignition electrodes are employed. Each flame sensing electrode is coupled to a switch which is tripped when the flame sensor no longer provides indication of a sensed flame. The switch in turn causes a spark generator to reignite the burner by producing a series of ignition sparks. Once a flame is once again sensed by the flame sensor, the sparking is stopped.
By optimizing the placement of the flame sensor based upon the conditions in which the burner will be operated, the likelihood of nuisance sparking is substantially reduced. Separate flame sensing electrodes also facilitate the provision of multiple flame sensors wired in parallel at strategic positions about the burner in order to further prevent random sparking at points of poor gas ignition or during flame waver.
These and other objects and advantages of the present invention will become apparent upon review of the following description taken in view of the accompanying drawings.